The invention relates to a method and apparatus for making a piece of tube from a flat web of flexible material, particularly paper coated with plastics, by grooving, stamping, cutting and folding, wherein the web is pulled off a storage roll and intermittently conveyed, and after folding over into tube form the longitudinal edges of the web are continuously interconnected by adhesion, welding or the like, and the web is severed.
Methods of the above type, for making packs, particularly for liquids, and apparatus for carrying out such a method, are known in the form of filling machines in the manufacture of liquid packs for milk or fruit juices. From a flat web of paper, coated with plastics on both sides and pulled intermittently off a storage roll, a tube is formed after grooving and stamping lines have been applied; the tube is filled with the liquid to be packed and is shaped into individual packs by welding means, after which individual pieces of tube, which are then divided from one another by transverse seams, are separated by cuts extending through these stamped lines.
It has been found that packs of this type can be made with large throughputs, with most packs of this known type being closed by folding and welding, both at the bottom and the top. The disadvantage here, however, is the space requirement with such manufacturing processes and machines, because great lengths are necessary for a flat web, drawn off a storage roll and driven continuously and possibly also intermittently, to be reshaped into a tube and for the tube to be formed by means of a longitudinal seam. In the known method extensive welding installations also have to be used, because once the tube has been made, i.e., when the longitudinal edges of the web have been joined together, it is filled with liquid at a subsequent stage. The liquid necessarily exerts a certain pressure on the pack surrounding it, and thus also on the new seam, so that without special welding equipment there would be a danger of the new seam bursting open.
In addition it has already been propposed to provide a pack with a lid or top made of plastics without supporting material, the pack thereafter being filled and only subsequently closed at the bottom by folding. To make such a pack, pieces of tube must be made in the shape of a cylindrical surface and put into an injection molding machine, in which the top component or lid with an opening is molded onto the cylindrical pieces of tube at one side. Molding onto cylindrical pieces of tube with large throughputs obviously creates insuperable difficulties for the expert; for one can hardly think of a machine with which pieces of tube can be shaped from a flat web with such precision that a desired matching internal dimension can be obtained, to which firstly a molding tool and secondly the molded piece of plastics can be fitted with its dimensions exactly matching.
The problem underlying the invention is to provide a method of making such a piece of tube from a flat web, and an apparatus for carrying out such a method as described more fully above, whereby the web of elastic, flexible material can be shaped into a tube and separated over a very short distance, while the piece of tube is very accurately dimensioned.
According to the invention the problem is solved in respect of the method, in that before the longitudinal edges of the web are joined, the web is partly incised at least from one longitudinal side, transversely to the conveying direction, that the tube is formed only by folding in these side sections divided by the incisions, that the non-incised part of the web is kept supported substantially flat, and that when the longitudinal edges of the web have been joined, their flat portion is severed in line with the incisions. The particularly novel idea of the invention is to leave the web of material at least partly in web form in one piece until the final severing, but to join together the longitudinal edges of the web, so that at least a partial tube is formed, before the final severing step, i.e., before the individual pieces of tube are separated. The tube is already divided, by the said incisions transversely to the longitudinal side of the web, into pieces which later form the length of the piece of tube produced. The shaping of a tube while the web of material partly remains in one piece is a process not hitherto known and allows for various treatments which were not previously possible in the formation of a tube.
For example, with the new method according to the invention, a piece of tube can be formed over a very short distance, if the web of material drawn off the reel is considered. Welding is also possible with very short welding times and the use of the simplest welding methods. This makes the desired pack considerably cheaper to produce.
In accordance with the invention it is further advantageous if incisions of approximately equal length are made in the flat web from both longitudinal sides, the inner end of the incisions extending as far as the grooved lines formed in the web, and if the sum of the areas of the side sections divided by the incisions is larger than the area of the central, flat portion of the web between successive pairs of incisions. The grooves can be made by the paper manufacturer. It is also possible, however, for the grooved lines to be made with the machine carrying out the method of the invention, at the beginning of the process described here. The grooved lines run in the direction in which the web is conveyed. They are used for folding in the side sections, formed by the incisions, onto the central, flat part of the web formed thereby. If one considers the piece of web which later becomes the piece of tube, between the successive pairs of incisions, then the area of the central flat part can be compared with that of the folded-over side sections. If the sum of the areas of the folded-over side sections is larger than that of the central part of the web, then the tubular cross-section formed will have one part slack and the other part curved. The curved part is that with the larger area, in the case of the present example with the side sections folded over. However, the longitudinal edges of the web, which have to be welded together, are on this part. Welding in this form is advantageously carried out without tension, and this is the reason why the simplest welding method can be used, with very short welding times and without any cooling time, preferably the use of constant contact heat. After the welding process there are in fact no forces in the web of paper or tensions therein which would put any appreciable strain on the new seam.
In a further advantageous embodiment of the invention, the side sections, which are folded in along the grooved lines and shaped as the piece of tube, are pressed together at one end adjacent the incisions to form a cone. It has been explained above that, when a lid is molded onto one end of a piece of tube, exact dimensions have to be observed if only for the sake of injection molding tools. It is also pointed out that it is extremely difficult to shape a tube or piece of tubing with exact internal dimensions, so that these could be drawn at all exactly onto a mandrel. But such a drawing action would be possible if, in accordance with the invention, the shape of the piece of tube were frusto-conical. To obtain the conical shape one end of the piece of tube must have a smaller diameter than the opposite end. Since the grooved lines can most simply be formed in the web if they run parallel with the web conveying direction, the above-mentioned measure according to the invention has to be carried out, namely, compressing the side sections at the appropriate end of the piece of tube in the region of the grooved line. If this compression takes place immediately before or during the welding process, the seam takes up the reduction in diameter, achieved by pressing together beyond the grooved line, and immediately fixes the reduction in diameter. In this way a slightly conical piece of tube is obtained in a very simple manner and in addition is partly still unseparated, i.e., is part of a web.
It is therefore advantageous if, in a further embodiment of the invention, after the severing of the flat part of the web the separated piece of tube is pushed aside transversely to the conveying direction of the web and stood upright to form a circular cross-section. The central part of the web which was kept flat gave the piece of tube a cross-section which was not previously not circular, e.g., substantially the cross-section of a segment of a circle. It is therefore favorable for the cross-section of the piece of tube to be erected at least approximately into the shape of a cylindrical surface after separation, i.e., after severing in line with the previously made incisions; one end of the cylinder, as mentioned above, having a slightly larger diameter than the other end, so that in an exaggerated description one could speak of a truncated cone. If the molding tool then has the shape of a tapered mandrel as the opposing molding tool, even a very slightly frustoconical tubular member could clearly easily be slid over the mandrel by appropriate ejection means, so that towards the end of the sliding process the narrow side of the truncated cone comes to rest really tightly over the front of the mandrel, i.e., with the appropriate dimensions fitting. This last described side of the mandrel is then a part of the injection mold, so that the halves of the tool can be placed very accurately around the end of the piece of tube.
In accordance with the invention, the apparatus for carrying out the method has cutting, feeding and folding means and is characterized in that a flat supporting plate, extending from the folding-in station to the severing station, is held stationary in the conveying direction of the web, in such a way that the web engages at least partly around it, that feed drive rollers are arranged above and below the web in the conveying directon, between the welding station which has at least one constant contact heating jaw, and the severing station which has a movable cutter, and that a distributing station with a means for standing the tube upright is arranged downstream thereof. With these measures it is possible to bring the web of flexible, elastic material, such as the web of paper coated on both sides used here to explain the invention, into the above-mentioned tubular shape with the segment shaped cross-section, by cutting and folding in. Part of the web lies under the supporting plate, while the two side sections folded over are arranged above it. This arrangement can be obtained if in accordance with the invention, the folding-in station has levers, which are rotatable about a spindle lying in the web conveying direction, and transverse mandrels, which are fixed to the levers and parallel with the spindle. When the web has been incised transversely to the longitudinal direction to form the side sections, the rotatable levers turn and swivel the transverse mandrels inwardly around the said spindle over the supporting plate, so that the plate is now almost completely surrounded by the web of material. With the continuous web being moved forwards intermittently or by degrees from the folding-in station to the succeeding welding preheating station, it may be desirable for the backing welding jaw to be arranged over the supporting plate and for the longitudinal edges of the web which have to be joined together to be slid over that jaw, while the transverse mandrels are still held in the swivelled-in position or holding rails maintain this tubular position of the web of paper. When the web is conveyed further into the welding station, the longitudinal edges to be joined together lie directly between the welding jaws in the desired manner, so that the tube can be formed, although part of the tube, in the form of the central flat region of the web, still remains part of the continuous web.
It is further desirable, according to the invention, for an adjustably displaceable incising means with a photoelectric cell controlling the drive rollers to be arranged before the folding-in station in the web conveying direction. In this way the apparatus can be adjusted to pieces of tube of different lengths. The distance between the line joining the two incisions and the photoelectric cell will remain the same in all embodiments, but the distance between this cutter or the photoelectric cell and the cutters of the severing station may be varied according to the necessary division of space or the number of pieces of tube therebetween. The apparatus can thus be adapted to different products by simple means.
It is also advantageous, according to the invention, for the welding station to have pressure jaws, arranged laterally adjacent the edges of the supporting plate and movable at a small angle of inclination thereto. In this way an exact internal dimension for the piece of tube can be obtained without a calibrating mandrel. It has already been mentioned above in the same connection that it is desirable to be able to make conical lengths of tubing, because a truncated cone can be drawn over a mandrel more easily than an exact cylindrical tube particularly if one considers that one end of the tube has to be placed with an exact fit over the end of the mandrel forming the casting mold member. The conical length of tubing can be made successfully with the movable pressure jaws mentioned. They are at a small angle of inclination, as seen in the web conveying direction--to the longitudinal side edges of the supporting plate. The jaws move perpendicularly to the web conveying direction. With their help it is thus possible for one end of the piece of tube, the front end as seen in the conveying direction, to be impinged on with a pressure against the edge of the supporting plate, while there is no pressure on the other side. As a result of this pressure the particular side wall section, formed by the incisions, adjacent the grooved line formed is pressed against the supporting plate, so that the tensions in the paper are thereby virtually eliminated. With the pressure jaws the paper is pressed virtually beyond its tension around the edge of the supporting plate, i.e., against resistance from the flat paper, because folding over takes place in the vicinity of the grooving and not in the grooved line itself. Since these movable pressure jaws are provided in the region of the welding station, the reduction in the diameter of the piece of tube at this location is immediately fixed by the welding process. It has been found in practice that a conical length of tubing can be obtained and manufactured very easily with these means, with part of the tubing still belonging to continuous webs, and that when the finished piece of tube has been severed and separated, an exact internal dimension is obtained without a calibrating mandrel; for the compression around the edges of the supporting plate takes place in such a controlled manner that exactly the desired internal dimension for the finished piece of tube is finally achieved.
It is also desirable, according to the invention, for at least one feed drive roller to have a central recess at the periphery. As seen in the conveying direction of the web the feed drive rollers are arranged behind the welding station. This does not provide any disadvantages in conveying the web, for the web extends continuously as far as the storage reel. The advantage of having the rollers arranged behind the welding station is that the drive rollers hold down the piece of tube, so that there is virtually a flat tube in cross-section, with the feed drive roller advantageously running directly over the welded seam. The above-mentioned central recess is provided to prevent the seam from being undesirably strained. Thus any stress on the seam, e.g., the occurrence of undesirable dislocations, is advantageously avoided. The so-called edge protector, which is a thin film in the region of the longitudinal seam, is also protected by the central recess, since otherwise with the line contact excessively high pressures might possibly be transmitted to the edge protecting film.
In another advantageous embodiment of the invention, connecting rails extending transversely to the web conveying direction are mounted in the distributing station and span the width of the supporting plate. Tube shaping members are fixed to the ends of the these rails, and a slide is guided movably between the rails. The slide is moved in cadence transversely to the web conveying direction, to the left or right, depending on the direction in which the piece of tube separated by the severing station is pushed aside. The throughput or machine output of the apparatus according to the invention can be considerably increased if the pieces of tube made from the web are divided into two methods of treatment, since then each method of treatment has more time for further processing, particularly when a lid or base is molded onto a piece of tube. Towards the end of each particular stroke the slide is always located outside the web and thus outside the width of the supporting plate, which of course is not absolutely necessary downstream of the severing station. It is more desirable for the tube or piece of tubing to be empty inside downstream of the severing station, so that the slide can push the tube aside without a great outlay on apparatus. It desirably pushes it into a tube shaping member at the appropriate side, with a circular diameter in cross-section, in which the piece of tube is then set upright into the desired shape. The slide may preferably assist in the erecting process by pressing into the end position. The next piece of tube will then be ready behind the severing station, so that the slide can reverse its direction of movement transversely to the conveying direction and push the next length of tubing in the opposite direction, into another tube shaping member, in which the same erecting process takes place as just described.
From the tube shaping member the length of tubing can be pushed in the direction of its longitudinal axis by ejectors onto the extruding mandrel already mentioned, where the further processing, initially the molding on of the lid, can take place.
In order to be able to locate an immovable or stationary blade or knife to provide the aforementioned incisions, rather than a cutter which is movable in the direction of delivery of the web, it is suitable if the incisions and the incising from the outer edge of the longitudinal web edges laterally to the conveying direction of the web towards the middle thereof are not made by a knife of a type, such as scissors, so that the incisions practically do not have their own width. Rather, it is more suitable if these lines, generally called "incisions", are made by punching. Thus, areas can be punched. Preferably the shape of these areas is longitudinal, i.e., instead of incsisions like a line also double line-incisions can be provided by punching out a narrow band.
In other words, using a punching knife, a strip-like portion of the web forming the incisions with the described depth towards the middle of the web can be removed, which strip has a width of 1 to 5 mm, preferably 2 to 3 mm. The assembly of a stationary knife or cutter is less expensive.
Therefore, a more simple severing station can be constructed in that as in the case of scissors, two blades are movable normally in the conveying direction of the web and facilitate the incising. However, a seeking of the two blades or a movement thereof in conveying direction of the web is not necessary.
If the punching strips are made already with the paper preparation, which strips then must not extend entirely to the outer edge of the web, then the incising means can provide the tolerance field necessary for the stationary severing knife also at the outer longitudinal edge of the web, provided the severing knife is a punching knife cutting off a partial area.
Further advantages, features and applications of the invention will emerge from the following desription of preferred embodiments, in conjunction with the accompanying drawings. In these: